I'm curious about Thermic Micro, as well. I've been comparing three very different bags that claim 30-32 degree ratings: Mountain Hardwear's Ultralamina 32, Sierra Designs' Lazer, and Montbell's UL Burrow Bag. Sierra Designs packs a respectable 20 oz. of Primaloft Sport into the Lazer, the lightest of the three bags (by an ounce). The Ultralamina has 18 oz. of Thermic Micro, but it also has a very appealing dual-zipper design. Finally, MontBell incorporates what I assume to be a very efficient gathered quilt design into the Exceloft-filled UL Burrow Bag (thanks for the follow-up, Dondo), but they don't publish the fill weight (I e-mailed MontBell America about this, but it would appear that they're unable to get the numbers from the engineers back in Japan).

Of the three, the Ultralamina would appear to be the most roomy (for layering), and the dual zipper design is very appealing. I assume that the Ultralamina also gets a thermal boost from the welded seams, but I'd really like to know more about how Thermic Micro compares to more widely used fills like Primaloft Sport or Polarguard Delta.

Richard, thanks for the Mars Space Suit link! It was very interesting. I did a google search to see who might be using the 4DG fiber for insulation in garments and didn't find any thing. Certainly someone must use it? Perhaps the marketing wonks have all renamed it for whatever reason. It looks very promising for wicking and for insulation.

You the man, Richard. Thanks for the Mars Space Suit link. It is interesting that "... Primaloft® Sport Albany Internationalwas chosen for evaluation owing to its high R value and ability to recover from compression."

Montbell: As Mitchell mentioned above, I think we can trust Montbell on the accuracy of their published weights and temperature ratings. He bases this on multiple reports from satisfied customers. Based on my own experience with a Montbell bag, I tend to agree. So the 32 to 34 oz. UL Burrow Bag #3 in definitely a candidate.

American sleeping bag manufacturers have an international reputation for assigning overly optimistic temperature ratings to their bags. Fortunately, we can correct for this by researching the European EN 13537 lower limit ratings for American bags.

TNF Orion: This Primaloft Sport bag gets a EN 13537 lower limit rating of 30F. It contains 26 oz. of insulation. Unfortunately, for 2007, TNF chose to include a foot zip and boosted the total weight of the bag to 40 oz. IMO, this was an unnecessary weight gain because the 2/3 zip gives plenty of room for regulating the warmth.

TNF Fission: No EN 13537 rating available. It has the same cut and a similar amount of insulation to the Orion. I'm guessing that this is a least a 30F bag. At a 34 oz. total weight, this Climashiled XP bag is a candidate if you're OK with the 1/3 zip.

Marmot Pounder Plus: This Primaloft Sport bag has a wider cut than the TNF bags. Insulation weight is 23 oz.; total weight 34 oz. But the EN13537 lower limit rating is 36F, so it may not be warm enough for folks looking for a true 30F bag.

Sierra Designs Lazer: Similar cut to the TNF Orion. But with 20 oz. of Primaloft Sport compared with 26 oz. for the Orion, I doubt that it would earn a EN13537 rating of 30F.

Sierra Designs Volt: This is more like it. With a similar cut to the Orion and Lazer but with 27 oz. of Primaloft Sport, I think this one would earn a EN13537 rating of at least 30F. Total weight is reported at 37 oz.

Mountain Hardware Ultralamina 32: OK, I'll admit that I have a bias against MH. This is based on the gross under reporting of the weight of some of it's shelters in recent years. Looking at the fill weight of 18 oz., I really doubt that this bag is could earn a EN13537 rating of 32F. Thermic Micro would have to be really, really special for them to pull this off.

As far as fill i have found that Thermic micro > Polarguard Delta > Primaloft. I didn't do much research into the effects of primaloft except that polaguard delta out performs it in loft retention 50% instead of 25% warmth to weight, primaloft is lighter but polarguard delta gets more bang for your buck and cold spot protection. It's variable laying technique and ability to stay together prevents cold spots. However, Thermic micro basically does everything polarguard delta does, better. It also has a surprisingly down-like feel compared to most synthetic because it's not laid in a woven sheet-like format. It almost looks like a bunch of twisted spaghetti noodles inside the shell, which further prevents cold spots and feels softer and retains more heat, like a down bag. I was comparing the MH ultralamina 15 degree sleeping bag to the North Face Cat's Meow 20 degree bag. The weight savings, warmth, and durability make this decision an no brainer after a little research. I'm not familiar with the two bag's you mention however, the Mountain Hardwear offers a nylon 20d ripstop with a DWR coating while the cat's meow is a polyester taffeta blend. The rip stop is more durable and repels water better, also the rip stop employs the box containment method, if it does get ripped the rip will stay confined in the boxes that it ripped preventing tearing. Also, it's welded seems prevent cold spots and water from entering the fill. The MH ultralamina was designed for wet climates and can repel precipitation and ///some/// puddling. I put it in a sink full of water and it did penetrate the shell, however within an hour it was cold/damp (not dry but most of the water had drained) and within three hours it was bone dry. However, it's a synthetic fill so even if it does get wet you wont loose it's insulating properties. Also, both of these bag's have vaulted footboxes which allow your feet to rest normally, however the ultra lamina has dual 1/3 zips meaning they only zip 1/3 of the way down, while the cat's meow has a full zip on the right side. The 1/3 zips are great on a cold night or if your cooking, reading, whatever, however if your warm it's nice to be able to unzip totally and let some air in. The MH ultralamina employs a face gasket and tailored hoot which offers a tight seal keeping body heat in and cold air out. The MH ultralamina is the no brainer for me as it compresses smaller, is lighter, warmer (yes i know one's a 15 one's a 20) and is more durable/water resistant. pike